This invention relates to the communication sub-system for communication between a gear shifter and a smart vehicle transmission. The communication sub-system makes use of existing industry standard or proprietary communication protocols and communication spines replace translation encoders now currently used to facilitate gearshift commands to the electronic control modules of smart transmissions. Smart vehicle transmissions have come into use mostly in commercial applications. Such vehicles appropriate for such installation include light, medium, and heavy duty trucks. This application is related to pending application Ser. No. 09/447,132, filed Nov. 22, 1999 and assigned to inventor""s assignee.
Smart vehicle transmissions are those with electronic control modules (ECMs) for receiving electronic signals directing gearshift position or mode of operation for automatic transmissions. The operator could operate the transmission or change the mode of the transmission by moving a gearshift in the cab of the vehicle. In contrast to automotive applications where the gearshift is mechanically engaged to operate or change modes of the transmission, the gearshift for a so-called smart transmission was in electronic communication with the transmission ECM through a dedicated line and an electrically inline encoder unit. This is shown in FIG. 5. Each smart transmission made by a different manufacturer requires its own unique shift control (lever or pushbutton control) or a separately programmed encoder unit. The different encoders were separately programmed for the specific transmission. The transmission ECM may additionally have been in communication with an engine ECM through a multiplexed communication network using an industry standard or proprietary protocol.
At a simple level, communication between two agents may be kept physically separated from communications occurring among other agents. Where two or more signals do not use the same physical space, there is no need to separate the signals in time or in carrier wave frequency. Such a communications regime is sometimes termed physical division multiplexing although the term multiplexing is usually reserved to techniques for applying multiple signals to a single medium or physical space. So-called physical division multiplexing describes how motor vehicles have been traditionally wired. The use of separate dedicated wires to connect each switch and lamp is a type of physical division multiplexing. Obviously, physical division multiplexing, while simple in concept, results in the use of many wires (the classical motor vehicle electrical harness), which are difficult to install during manufacturing and problematic to maintain in the field.
Arrangements allowing a number of agents to communicate over a common physical layer or medium offer much greater physical simplicity. Intelligible communication between two or more devices among a greater plurality of devices, all over a common medium, depends upon the communicating devices being able to distinguish, and understand, messages directed to them from other messages which they receive, but which are not intended for them. The process of distinguishing messages depends upon the transmitter of the message applying some attribute to the message which identifies it to the intended recipient. In human conversation, most people readily distinguish speech directed to them from interfering cross-talk in a crowd by the distinctive aspects of the voice of the person addressing them. Where the members of the group are electrical components, the problem still involves identification of a distinguishing attribute of the signal. Appropriate attributes for signals take a number of forms.
A line communicating a signal from a remote switch to a lamp to turn on or off (by having a second switch, local to the lamp, change states to control connection of the lamp between a power bus and ground) cycles only rarely. In a typical trip such a change in state occurs only once or twice, if at all. Where such a line is not intended to provide power to the lamp, and simply indicates changes in state for the local switch controlling the lamp, the line will have the capacity to handle far more data than the occasional indications to turn a lamp on and off. The objective of maintaining simplicity in manufacturing and maintenance are preferably met by allowing communication among a number of components to occur in a single medium, or at least as few communication lines as possible. The line used to connect switch and lamp could interconnect a number of components, carrying messages between any grouping of elements connected to the line when not required to carry an instruction to a lamp to turn on. One way of achieving this objective is a communications regime that divides time into slots during which particular combinations of components have use of a signaling line. Such methods are well known in the art and are examples of time division multiplexing (TDM). In motor vehicles, time division and related multiplexing techniques offer substantial simplification in physical layer required to support the control of vehicle vocations.
Rigid time division multiplexed communications appear to interleave data signals into a single serial signal over a single physical medium. Multiplexed communication systems also provide the reverse function (de-multiplexing) of dividing the single signal into multiple, non-synchronous digital signals. Where demands on the capacity of the data transmission medium are not especially heavy, any unit may be allowed to claim the medium provided collision detection is provided for and other indicia, such as address headers, indicate the signal""s destination.
As applied to motor vehicles, multiplexed communications over serial data paths are an effective technique for reducing the number of dedicated communication paths between the numerous switches, sensors, devices and gauges installed on the vehicles. With each increase in the number and variety of accessories and functions installed on each vehicle, the benefits of using a single, multiplexed communication serial link for passing instructions to and receiving information from vehicle devices as diverse as running lights and rear axle temperature sensors becomes greater. Multiplexing the signals to and from local controllers and switches for vehicle systems promises greater physical simplicity through displacing much of the vehicle wiring harness, reducing manufacturing costs, facilitating vehicle electrical load management, and enhancing system reliability.
The specific manner of implementing multiplexed communications is outside the scope of the present invention, which applies a defined protocol, the SAE J1939 protocol. Additionally, proprietary protocols may be used although over a network similar to as described here. The development by the Society of Automotive Engineers of the J1939 series of standards for multiplexed communications testifies to the progress in the application of multiplexed communications to vehicles. Standards have been or are being developed relating the communication path, transmission collision detection, diagnostic ports and data protocols, among other topics. The J1939 protocol provides an open protocol and definition of the performance requirements of the medium of the physical layer, but also allows for development of proprietary protocols. The SAE J1939 protocol is a specialized application of a controlled area network (CAN) and may be readily implemented utilizing commercial integrated circuits such as the C167 Integrated Circuit from Siemens of Germany.
A serial communications system utilizing a multiplexing regime can link several remote digital controllers positioned around a vehicle with an electrical system controller (ESC) for two way communication. Remote digital controllers are addressable, allowing them to respond to signals intended for them initialize particular functions. As described above the transmission ECM may be a remote digital controller. They may also include programming that allows the device to react to local conditions as well as condition indicating signals provided the controller. The ESC may pass requests and instructions received for operations of certain devices, addressed to the correct remote controller, in a fashion to condition the timing and duration of the responses to requests to better manage overall vehicle electrical load.
What is needed and does not exist in the prior art is a transmission and gearshift subsystem or a vehicle which such a system that does not require a separate encoder and separate dedicated communication line dedicated to electrical signals between a gearshift and a smart electronic transmission controller.
An object of the invention is to provide a transmission and gearshift subsystem for a mobile vehicle that does not require a separate encoder in series between the gearshift and the electronic transmission. This should at a minimum save on the cost of having the encoder. A second object of the invention is to provide for communications between the gearshift and the electronic transmission without the need for a dedicated electrical communication line. A third object of the invention is provide an embodiment of a communication sub-system for communications between the gearshift and the electronic transmission that uses an industry standard protocol rather than proprietary commands limited to the specific transmission manufacturer.
The transmission and gearshift communication sub-system and vehicle with the subsystem installed of this invention satisfies all the objects of the invention and others not mentioned. Rather than have a separate dedicated line between the electronic gearshift and the electronic transmission, the communication subsystem of this invention involves electrically connecting both the gearshift and the transmission ECM to a common vehicle network. The network may allow communication by an industry standard, such as J1939, or by a proprietary protocol. The key point is that the gearshift and transmission ECM are both tied into a common network to communicate using a standard protocol. There may be other digital controllers engaged to the network for communication. The transmission ECM will receive electronic messages for manual transmission control or transmission mode change (i.e. Park, Reverse, Neutral, Economy, Hold) in signals according to the standard protocol through the common network from the gearshift upon operator manipulation of the gearshift. No special dedicated line between the gearshift and the transmission will be required. Additionally, there will be no encoder module to translate instructions from the gearshift because the gearshift will communicate via a standard protocol to the transmission ECM. It should be noted that transmission ECMs already communicate with vehicle engine ECMs using such standard protocols as J1939 so receiving instructions from the gearshift will be a minor programming effort. A drawing of a sample vehicle electronic communication sub-system for communication between a gearshift and an electronic transmission is shown. Additionally, such a sub-system as part of a vehicle wide network is also shown in a second figure.
Additional effects, features and advantages will be apparent in the written description that follows.